The British Lions will not make a final decision on the fitness of Alex Corbisiero, Mike Phillips and Jamie Roberts until Wednesday.
Tour manager Andy Irvine insisted that all three were making progress and that the Lions medical team remain hopeful of their inclusion for the third Test.
Roberts has been out since the win over the Waratahs three weeks ago, whilst Corbisiero and Phillips missed the second Test after playing in the Lions' victory in Brisbane.
"We're hoping that they will be ready. The final decision won't be taken until Wednesday," said Irvine.
"They are all making good progress. The medics are reasonably hopeful.
"It's a serious blow because Sam started the tour with a knee injury but got better as the tour progressed.
"In the first half he was the outstanding player on the park. He's extremely disappointed that he's not available.
"On the positive side we're fortunate that it's one of the positions where we have tremendous reserve strength.
"We feel for Sam, he's been a super captain and role model to the lads. Hopefully we can go out and win the third Test for him."